This competing continuation proposes to conduct the second phase of a research project to create and evaluate a novel computer-based tobacco prevention program for 5th and 6th grade students that is effective, disseminable and highly engaging. The purpose of this prevention program is to decrease children's behavioral intentions and willingness to use tobacco, and to prevent or delay their initiation of tobacco use. The program is innovative in that it is delivered over a school-based intranet (networked computers linked to a common server), which allows experiential learning and immediate feedback on classmates'responses, and it is translational in nature. Program components are iteratively developed and evaluated to assure that they are effective at changing theoretically-based mediating mechanisms derived from the Prototype/Willingness model and affect-based risk perception and decision theory. The final program addresses statewide tobacco prevention objectives. Phase 1 of this project, a 3-year developmental study, is nearing completion. We have created an exciting 3-D environment as the interface of the program, developed and demonstrated the effectiveness of 12 components for the 5th grade program, and anticipate successfully completing the final 5 components and conducting a field test within the next few months. The aims of Phase 2, proposed here, are to: (1) Conduct a randomized efficacy trial in schools to assess the effectiveness of the program;(2) Iteratively develop and test the effectiveness of 7 components to include in the 6th grade booster sessions;(3) Develop a program guide for teachers and parent newsletters;(4) Examine change from 5th to 7th grade in the mechanisms that the TFT program is designed to target, and assess if these cognitive mechanisms serve to mediate the effects of the program on smoking outcomes. The efficacy trial will be conducted with 3,225 children in 44 elementary and 22 middle schools in 6 counties in Western Oregon using computers and technical support supplied by the project. Baseline and follow-up student assessments will be conducted by project staff in 5th, 6th, and 7th grades. Public health relevance. There is a substantial increase in smoking initiation between grades 4 and 5 and grades 6 and 7, making this developmental period an ideal time to deliver a tobacco prevention program. The goal of this program is to prevent children from becoming more susceptible to smoking during this vulnerable period. Consistent with the mission of NCI, preventing or delaying early smoking initiation leads to less adult smoking and nicotine dependence and, correspondingly, to substantial health benefits. Translating contemporary theories about why children are willing to try smoking and why positive feelings about smoking reduce its perceived risk has resulted in the development of novel and effective program components demonstrated individually to change these tendencies. Phase 2 will capitalize on the success of Phase 1 by evaluating the efficacy of the completed program, which has enormous potential for future dissemination nationwide,